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| United States Patent |
6,117,685
|
|
Omatsu
, et al.
|
September 12, 2000
|
Ozone indicator and ozone detecting ink
Abstract
The invention provides a method of detecting ozone expediently and with
high sensitivity. The invention, therefore, is directed to an ozone
indicator comprising (1) at least one color-change layer comprised of an
ozone sensor ink and (2) at least one non-color change layer both formed
on a substrate, said color-change and non-color-change layers being formed
in such a manner that at least a part or the whole of at least one
color-change layer can be exposed to an ozone-containing atmosphere when
the ozone indicator is put to use. The invention is further directed to an
ozone sensor ink containing an anthraquinone dye having at least one amino
group selected from primary and secondary amino groups.
| Inventors:
|
Omatsu; Takeshi (Kyoto-fu, JP);
Inoue; Hiroshi (Osaka-fu, JP)
|
| Assignee:
|
Sakura Color Products Corporation (Osaka-fu, JP)
|
| Appl. No.:
|
083953 |
| Filed:
|
May 22, 1998 |
Foreign Application Priority Data
| May 22, 1997[JP] | 9-132652 |
| Sep 01, 1997[JP] | 9-236347 |
| Nov 11, 1997[JP] | 9-308774 |
| Current U.S. Class: |
436/135; 422/56; 422/57; 422/86; 422/87; 436/169; 436/170 |
| Intern'l Class: |
G01N 031/22 |
| Field of Search: |
436/135,164,166,169,170,810
422/56,57,86,87
|
References Cited
U.S. Patent Documents
| 3397966 | Aug., 1968 | Plantz.
| |
| 3568627 | Mar., 1971 | Selinger et al.
| |
| 3704096 | Nov., 1972 | Verses et al.
| |
| 3914174 | Oct., 1975 | Fuchs.
| |
| 4772560 | Sep., 1988 | Attar.
| |
| 4859607 | Aug., 1989 | Lambert et al.
| |
| 5178831 | Jan., 1993 | Sakota et al.
| |
| 5281662 | Jan., 1994 | Ito et al.
| |
| 5480611 | Jan., 1996 | Mills et al.
| |
| 5480702 | Jan., 1996 | Matsumoto et al.
| |
| 5667572 | Sep., 1997 | Taniguchi et al.
| |
| 5722322 | Mar., 1998 | Watanabe.
| |
| Foreign Patent Documents |
| 196 16 226 | May., 1996 | DE.
| |
| 62-291564 | Dec., 1987 | JP.
| |
| 5-165254 | Jul., 1993 | JP.
| |
| 6-082410 | Mar., 1994 | JP.
| |
| 9-220277 | Aug., 1997 | JP.
| |
Primary Examiner: Beisner; William H.
Attorney, Agent or Firm: Knobbe, Martens, Olson & Bear, LLP
Claims
What is claimed is:
1. An ozone indicator comprising (1) at least one color-change layer
comprised of an ozone sensor ink which contains an anthraquinone dye
having at least one amino group selected from primary and secondary amino
groups and (2) at least one non-color-change layer both formed on a
substrate, said color-change and non-color-change layers being formed in
such a manner that at least a part or the whole of at least one
color-change layer can be exposed to an ozone-containing atmosphere when
the ozone indicator is put to use.
2. The ozone indicator of claim 1 wherein the color-change layer and the
non-color-change layer are formed in such a manner that a discernible
color difference occurs between the color-change layer and the
non-color-change layer only after the color-change layer has undergone
change in color.
3. The ozone indicator of claim 1 wherein the color-change layer and the
non-color-change layer are formed in such a manner that at least one of
character, pattern and code designs appear only after the color-change
layer has undergone change in color.
4. The ozone indicator of claim 2 or 3 wherein the color-change layer
before color change and the non-color-change layer are substantially of
the same color.
5. The ozone indicator of claim 1 wherein the color-change layer and the
non-color-change layer are formed without overlap of the layers.
6. The ozone indicator of claim 1 further comprising an additional
color-change or non-color-change layer on at least one of said
color-change layer and non-color-change layer.
7. The ozone indicator of claim 1 further comprising a means for placing at
least the color-change layer under constant ambient atmospheric
conditions.
8. The ozone indicator of claim 1 wherein the ozone sensor ink further
comprises a cationic surfactant of the quaternary ammonium salt type.
9. The ozone indicator of claim 8 wherein the cationic surfactant of the
quaternary ammonium salt type is an alkyltrimethylammonium salt.
10. The ozone indicator of claim 1 wherein the ozone indicator ink further
comprises an extender.
11. The ozone indicator of claim 1, wherein the ozone indicator ink further
comprises a resinous binder.
12. A method of measuring the concentration of ozone which comprises
installing the ozone indicator claimed in claim 1 in an ozone-containing
atmosphere and determining the color difference produced by color change
of the color-change layer or the CT value based on the zone of said color
change.
13. The method of claim 12, wherein at least the color-change layer is
placed under constant ambient atmospheric conditions.
14. A method of determining concentration of ozone in an ozone-containing
atmosphere, comprising: (i) applying on a substrate an ozone sensor ink
comprising an anthraquinone dye having at least one amino group selected
from primary and secondary amino groups; (ii) detecting a change in color
of the ozone sensor ink after a predetermined time period; and (iii)
determining the concentration of ozone in the atmosphere based on the
change.
Description
FIELD OF THE INVENTION
The present invention relates to an ozone indicator and an ozone sensor
ink.
BACKGROUND OF THE INVENTION
Ozone, by virtue of its high germicidal and other actions, has been
utilized for the sterilization and disinfection of foods and instruments
or sterilization, disinfection or deodorization of the atmosphere in
confined spaces such as the operation theaters of hospitals. On the other
hand, ozone is so toxic and deleterious to human health that there is
naturally an allowable limit to its concentration. Meanwhile, in
photochemical smog forecasts, the atmospheric oxidant level is a
significant factor.
For the monitor of ozone concentration, therefore, a variety of methods
have been developed for its detection. The principal ozone (oxidant)
detection technology available so far takes advantage of the color change
according to the following reaction scheme (1).
##EQU1##
As specific detection methods utilizing the above principle, the optical
method which comprises introducing an ozone-containing gas into a solution
of potassium iodide and measuring the degree of resultant color change,
which is proportional to the amount of liberated iodine, by means of a
calorimeter and the expedient method utilizing a simple sensor tube are
known.
However, the above optical method is not only complicated procedure-wise
but time-consuming, failing to provide real-time data. Moreover, the
equipment for practicing the method is very expensive. Particularly when a
multi-point simultaneous determination is necessary, a plurality of
devices must be installed so that the cost adds up to an enormous sum.
The method using a sensor tube is more expedient than the optical detection
method. However, the method is still costly and it is necessary to
aspirate the oxidant manually or automatically at each determination.
Thus, regardless of which of those known methodologies is utilized, there
remains to be developed an expedient and sensitive method for detecting
ozone.
SUMMARY OF THE INVENTION
Developed in the above state of the art, the present invention is directed
to the following ozone indicator and ozone sensor ink.
1. An ozone indicator comprising (1) at least one color-change layer
comprised of an ozone sensor ink and (2) at least one non-color-change
layer both formed on a substrate in such a manner that a part or the whole
of at least one-color-change layer can be exposed to an ozone-containing
atmosphere when the ozone indicator is put to use.
2. An ozone sensor ink comprising an anthraquinone dye having at least one
amino group selected from primary and secondary amino groups.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing an example of the ozone indicator comprising a
color-change layer covered with a transparent resin sheet.
FIG. 2 is a view showing an example of the ozone indicator comprising a
color-change layer formed on one inner side of a transparent housing.
FIG. 3 is a view showing the design printed in the ozone sensor ink in
Examples 4 and 5.
FIG. 4 is a view showing the design printed in a regular color ink in
Examples 4 and 5.
FIG. 5 is a view showing the design printed in the ozone sensor ink in
Example 6.
FIG. 6 is a view showing the design printed in a regular color ink in
Example 6.
FIG. 7 is a view showing the design printed in the ozone sensor ink in
Example 6.
FIG. 8 is a view showing the design printed in a regular color ink in
Example 7.
DETAILED DESCRIPTION OF THE INVENTION
The ozone indicator of the present invention comprises (1) at least one
color-change layer comprised of an ozone sensor ink and (2) at least one
non-color-change layer both formed on a substrate in such a manner that a
part or the whole of at least one color-change layer can be exposed to an
ozone-containing atmosphere when the ozone indicator is put to use.
The color-change layer is a layer adapted to undergo change in color in the
presence of ozone, and is chiefly comprised of an ozone sensor ink. On the
other hand, the non-color-change layer is a layer which does not undergo
change in color even in the presence of ozone and is formed using an ink
which does not respond color-wise to ozone. In the present invention, the
non-color-change layer even includes a substrate itself provided that the
substrate does not undergo change in color in the presence of ozone.
Therefore, for example, the indicator comprising a color-change layer
comprised of an ozone sensor ink formed on a substrate which does not
undergo change in color in the presence of ozone is also a species of the
ozone indicator of the invention. Moreover, an ozone indicator fabricated
by impregnating a substrate not color-wise responding to ozone (paper,
nonwoven cloth, etc.) with an ozone sensor ink can also be used as the
ozone indicator of the invention. Particularly, for a good discernibility
of color change and a greater freedom in design, the non-color-change
layer is preferably comprised of an ink which does not undergo change in
color upon exposure to ozone.
In fabricating the ozone indicator of the invention, the color-change layer
and the non-color-change layer may be formed each as a single layer or a
plurality of superimposed layers. Moreover, a color-change layer may be
disposed immediately on another color-change layer or a non-color-change
layer may be formed on top of another non-color-change layer. In such
cases, the plurality of color-change layers may be of the same composition
or different compositions. Similarly, the plurality of non-color-change
layers may be of the same composition or different compositions.
The color-change layer and the non-color change layer may be formed either
on the whole surface or only locally on the surface of a substrate or
another layer. For insuring a positive color change of the color-change
layer, the color-change and non-color change layers are formed in such a
manner that a part or the whole of at least one color-change layer is
directly exposed to an ozone-containing atmosphere.
For partial exposure of the color-change layer to an ozone-containing
atmosphere, there are several alternative methods which can be used, e.g.
the method of forming a non-color-change layer on a color-change layer
leaving at least a part of the color-change layer exposed, the method
which comprises covering a part of the color-change layer with a cover
member made of a known material such as a plastic or glass leaving the
remaining part exposed, or the method which comprises forming a
color-change layer on a part or the whole of one inner side of a housing
provided with at least one opening. The structure obtainable by any of the
above and other methods is invariably subsumed in the concept of the ozone
indicator of the invention.
There is no particular limitation on the shape or geometry of said member
or housing provided that the presence of ozone may be detected. Thus, for
example, members of known configurations such as the plate, disk, sheet,
etc. and housings of known geometric variations such as the cube, square
rod, cylinder, etc. can be mentioned. The material of such a member or
housing can be judiciously selected according to the objective of
determination and the measuring environment, among other conditions.
Particularly preferred are transparent materials such as acrylic resin,
celluloid resin, and glass. When a transparent material is used, the zone
of color change, color difference, etc. can be easily recognized and
assessed from outside. Therefore, provided that this discernibility is
satisfied, the material may be colorless and transparent, colored and
transparent, or even translucent.
The indicator comprising a color-change layer covered with a known cover
member may for example be the indicator illustrated in FIG. 1, that is an
indicator comprising a substrate (1) saturated with an ozone sensor ink
and a transparent resin sheet (2) as disposed on said substrate. The
substrate and the transparent resin sheet are connected to each other with
a supporting means (3). The supporting means is not restricted in kind
provided that it is capable of supporting the substrate and the
transparent resin sheet. Thus, for example, the known cement, adhesive,
metal fastener, etc. can be used. In an ozone-containing atmosphere, a
color change begins in that part of the color-change layer which is not
covered with the transparent resin sheet. Then, ozone diffuses through the
clearance between the transparent resin sheet and the substrate or into
the substrate gradually to cause the front of color change to advance
toward the central part of the substrate. Thus, by using a construction
such that the degree of exposure to ozone varies continuously, it is
possible to have a zone of color change formed in the color-change layer
and accordingly assess the ozone concentration either quantitatively or
qualitatively according to the size or configuration of said zone of color
change. In this connection, because the member covering the color-change
layer is a transparent resin sheet, the zone of color change can be easily
recognized from outside.
The above-mentioned indicator of the housing type may for example be the
indicator illustrated in FIG. 2, which comprises a transparent rectangular
housing provided with at least one opening (1) and a color-change layer
(2) formed by coating an inner side of the housing with an ozone sensor
ink. In this indicator, the color change begins to occur in that part of
the color-change layer which is adjacent to the opening and progresses
inwards gradually. In this case, too, the ozone concentration can be
assessed quantitatively or qualitatively according to the size of the
color change zone developed in the color-change layer. In addition,
because the rectangular housing is made of a transparent material, the
zone of color change can be easily recognized from outside. Incidentally,
insofar as the color change can be recognized, only a portion of the
housing may be transparent. The side of the housing on which the
color-change layer is formed is preferably opaque and of a color different
from the color that is developed in the color-change layer.
Where necessary, the indicator of the invention may be provided with a
means for placing the color-change layer under constant ambient
atmospheric conditions. In the present invention, such means includes
means for establishing a substantially wind-free condition and means for
supplying a wind of constant volume to the color-change layer. The
specific means for establishing a substantially wind-free condition may
for example comprise installing a wind-shielding device such as a hood so
that the color-change layer may be protected from a direct draft of air.
The means for sending a wind of constant volume may comprise using a known
blower. The type of blower is not particularly restricted provided that it
is capable of supplying a constant wind and may for example be a
commercial fan or a commercial dryer, or any other known device that is
functionally equivalent thereto. In accordance with the invention, insofar
as the color-change layer may be placed under constant atmospheric
conditions, such a wind shielding device or a blower means may be
installed externally of the indicator of the invention. In the sense that
the concentration of ozone can be rapidly and accurately measured, it is
preferable to employ a means of sending a constant wind to the
color-change layer.
The indicator of the invention, when used in association with a means for
placing its color-change layer under constant ambient atmospheric
conditions, provides for a more accurate and rapid detection of ozone
concentration and CT (ozone concentration.times.exposure time) values. In
this sense, the indicator of the invention can be used in various
atmospheric environments such as the place where an air conditioner or
circulator is available and a windless place which is protected from
external disturbances.
Particularly, in accordance with the invention, the ozone concentration and
CT can be qualitatively or quantitatively determined from the color
difference, the size of the color change zone etc. based on the known data
on the relationship of CT with color difference (.DELTA.E), the
relationship of CT with the size of the color change zone and the like.
For example, by providing graduations corresponding to CT values in the
vicinity of the color-change layer of the ozone indicator of the
invention, the CT can be determined quantitatively according to the size
of the color change zone of the color-change layer. Furthermore, based on
the CT value so found, the ozone concentration or the exposure time can be
quantitatively or qualitatively determined.
In the present invention, the color-change layer and the non-color-change
layer can be formed in such a manner that the color difference between the
color-change layer and the non-color-change layer can be recognized only
after change of color of the color-change layer or that the color
difference between the color-change layer and the non-color-change layer
is abolished upon color change of the color-change layer. It is
particularly recommendable to form the color-change layer and the
non-color-change layer in such a manner that the color difference between
the color-change layer and the non-color change layer is discernible only
after change of color of the color-change layer.
In connection with the discernibility of a color difference, the
color-change layer and the non-color-change layer may be formed in such a
manner that at least one of character, pattern and code designs will
appear only after change of color of the color-change layer. In the
present invention, the character, pattern and code designs include all
designs capable of informing a change in color (i.e. the presence of
ozone). Such character and other designs can be liberally selected
according to the intended application.
In addition, the color of the color-change layer before color change and
the color of the non-color-change layer may be dissimilar or such that
whereas both layers are of the same color, a discernible color difference
(contrast) occurs upon color change of the color-change layer.
In the ozone indicator of the invention, the color-change layer and the
non-color change layer may be formed in such a manner that the two layers
will not overlap. By so dosing, savings can be realized in the necessary
amount of the ink. For example, the color-change layer may be formed on a
part of the substrate, with the non-color-change layer being formed on the
remaining part or the remaining part of the substrate being left exposed.
As a further embodiment of the present invention, another color-change
layer or non-color-change layer may be formed on at least one of said
color-change layer and non-color change layer. For example, when another
color-change layer of a different design is formed on top of a layer
(=color-change/non-color-change layer) formed by disposing a color-change
layer and a non-color-change layer in non-overlapping relation, the
borderline between the color-change layer and non-color-change layer of
the color-change/non-color change layer can be made substantially
non-discernible and, hence, a better appearance can be obtained.
The kind of substrate that can be used for the ozone indicator of the
invention is not particularly restricted provided that said color-change
layer and non-color-change layer can be successfully formed. For example,
metals and alloys, wooden materials, paper, ceramics, glass, concrete,
plastics, and fibers (nonwoven fabrics, woven fabrics, and other webs or
sheets), inclusive of their composites can be mentioned.
The ozone sensor ink for use in the fabrication of said color-change layer
is not restricted provided that it undergoes change in color on exposure
to an ozone-containing atmosphere but may be a known ink or even a
commercial ink. For example, inks prepared by using potassium iodide, a
triphenylmethane leuco dye, p-n-butoxyaniline or the like can be used. In
the context of the present invention, "color change (or change in color)"
is a comprehensive term meaning any and all changes in an initial color
(in brightness, hue, etc.), thus including but not limited to fading,
discoloration and color development.
In the present invention, it is preferable to use an ink containing an
anthraquinone dye having at least one amino group selected from primary
and secondary amino groups.
The anthraquinone dye for use in the present invention is not restricted to
any specific species provided that it has an anthraquinone nucleus and at
least one amino group selected from primary and secondary amino groups.
The known anthraquinone disperse dyes can also be used. The dye may have
two or more amino groups of the same kind or different kinds.
The anthraquinone dye as such includes but is not limited to
1,4-diaminoanthraquinone (C. I. Disperse Violet 1),
1-amino-4-hydroxy-2-methoxyanthraquinone (C. I. Disperse Red 4),
1-amino-4-methylaminoanthraquinone (C. I. Disperse Violet 4),
1,4-diamino-2-methoxyanthraquinone (C. I. Disperse Red 11),
1-amino-2-methylanthraquinone (C. I. Disperse Orange 11),
1-amino-4-hydroxyanthraquinone (C. I. Disperse Red 15),
1,4,5,8-tetraaminoanthraquinone (C. I. Disperse Blue 1), and
1,4-diamino-5-nitroanthraquinone (C. I. Disperse Violet 8) etc.
[proprietary dye numbers in parentheses]. In addition, dyes known as C. I.
Solvent Blue 14, C. I. Solvent Blue 63, C. I. Solvent Violet 13, C. I.
Solvent Violet 14, C. I. Solvent Red 52, C. I. Solvent Red 114, C. I. Vat
Blue 21, C. I. Vat Blue 30, C. I. Vat Violet 15, C. I. Vat Violet 17, C.
I. Vat Red 19, C. I. Vat Red 28, C. I. Acid Blue 23, C. I. Acid Blue 80,
C. I. Acid Violet 43, C. I. Acid Violet 48, C. I. Acid Red 81, C. I. Acid
Red 83, C. I. Reactive Blue 4, C. I. Reactive Blue 19, C. I. Disperse Blue
7, etc. can also be employed. Those anthraquinone dyes can be used each
independently or in combination. Preferred among those anthraquinone dyes
are C. I. Disperse Blue 7 and C. I. Disperse Violet 1. Furthermore, in the
practice of the invention, the ozone detection sensitivity can be
controlled by modifying the description (e.g. molecular structure) of
those anthraquinone dyes.
In the practice of the invention, the ink containing such an anthraquinone
dye as above is more preferably supplemented with a cationic surfactant of
the quaternary ammonium salt type.
The cationic surfactant of the quaternary ammonium salt type (hereinafter
sometimes referred to briefly as "cationic surfactant") is not
particularly restricted. Alkylammonium salts are usually selected and
commercial products can be used for the purpose. Moreover, such
surfactants can be used each independently or as a mixture of two or more
species. In the present invention, an improved ozone detection sensitivity
can be obtained by using such a cationic surfactant in combination with
said anthraquinone dye.
Preferred among such cationic surfactants are alkyltrimethylammonium salts
and dialkyldimethylammonium salts. Specifically,
coco-alkyltrimethylammonium chloride, tallow-alkyltrimethylammonium
chloride, behenyltrimethylammonium chloride, hexadecyl-trimethylammonium
chloride, lauryltrimethylammonium chloride, octadecyltrimethylammonium
chloride, dioctyl-dimethylammonium chloride, distearyldimethylammonium
chloride, alkylbenzyldimethylammonium chloride, etc. can be mentioned.
Particularly preferred is lauryltrimethylammonium chloride.
The ink for the present invention may be supplemented with various
formulating agents such as those incorporated in known inks, for example a
resinous binder, an extender, a solvent, and so forth.
The resinous binder can be judiciously selected according to the type of
substrate, for instance, and the known component resins included in
writing or printing ink compositions can be used as such. To mention some
specific examples, maleic acid resin, amide resin, ketone resin,
alkylphenol resin, rosin-modified resin, poly(vinyl butyral),
poly(vinylpyrrolidone), and cellulosic resin can be used.
The extender is not particularly restricted but includes bentonite, active
terra alba, aluminum oxide, silica gel, and so forth. Aside from the
above-mentioned extenders, various substances known as extender pigments
can also be used. Particularly preferred, among them, are porous
extenders. Silica gel, in particular, is still more preferred. By adding
such an extender, the detection sensitivity, in the main, can be
controlled.
The solvent species which can be used in the present invention includes all
those solvents which are generally used in printing or writing ink
compositions. For example, solvents in the alcohol series, ester series,
ether series, ketone series, and hydrocarbon series can be selectively
used according to the solubility of the dye and resinous binder, among
other parameters.
The amounts of those formulating agents can be judiciously selected
according to their kinds and the intended uses. For example, when an ink
containing said anthraquinone dye is used as the ozone sensor ink, the
usual concentration of the anthraquinone dye in the ink may range from
0.05 to 5 weight % (preferably 0.1-1 weight %) and this basal formulation
may be adjusted with 50 weight % or less (preferably 5-35 weight %) of
said resinous binder and 1-30 weight % (preferably 2-20 weight %) of said
extender.
When a cationic surfactant is added, the usual formulation may be 0.05-10
weight % (preferably 0.1-1 weight %) of the anthraquinone dye, 0.2-30
weight % (preferably 0.5-10 weight %) of the cationic surfactant and this
basal formulation may be adjusted with 50 weight % or less (preferably
5-35 weight %) of said binder and 1-30 weight % (preferably 2-20 weight %)
of said extender.
Those components can be added at one time or sequentially and evenly
blended using a known mixing machine such as a homogenizer, a dessolver,
or the like. An exemplary procedure comprises adding the anthraquinone
dye, cationic surfactant, resinous binder, and extender serially to the
solvent and mixing them together under agitation.
On the other hand, as the ink for said non-color-change layer, any ink can
be used provided that it does not undergo change in color upon exposure to
ozone. As the ink as such, commercial regular inks can be used. For
example, water-based inks, oil-based inks, solventless inks, etc. can be
mentioned. In the case of printing, the known relief printing ink, gravure
printing ink, screen printing ink, offset printing ink, etc. can be
selectively used according to the printing method adopted. Those inks can
be used each independently or as blended for color mixing. It should be
understood that the ink for the non-color-change layer may contain those
components which are usually included in known inks (e.g. resinous binder,
extender, solvent, etc.).
The formation of the color-change layer and non-color-change layer in the
present invention can be carried out by the known printing techniques such
as silk screen printing, gravure printing, offset printing, relief
printing, flexo printing, etc. using inks suited for the respective
techniques. The order of printing for the color-change layer and the
non-color-change layer is not critical and can be chosen according to the
design to be printed. Those layers can be respectively formed by dipping
the substrate in the respective inks. This technique is particularly
suited for substrates which are permeable to the ink, such as paper and
nonwoven fabrics.
According to the ozone indicator of the invention, comprising a specific
combination of color-change and non-color-change layers, the color change
can be detected accurately, thereby the presence of ozone can be recognizd
easily. Furthermore, when the whole architecture of the indicator is a
sheet or a board, it does not take space and, when a judicious substrate
is chosen, is flexible, so that it can be installed in any desired
position or location.
Furthermore, by adopting a judicious combination of said color-change and
non-color-change layers, the pattern, character and code designs pertinent
to intended applications can be represented so as to impart an
aesthetic/functional value and insure a versatility of use.
Moreover, by adopting an architecture such that the progress or degree of
exposure to ozone is expressed continually as typically illustrated in
FIGS. 1 and 2, the ozone concentration and CT can be qualitatively or
quantitatively assessed according to the size of color change zone and/or
the color difference.
When the ozone sensor ink of the invention is used in the formation of the
color-change layer, it reacts effectively with ozone to undergo change in
color even when it is in a substantially dry condition, insuring still
more improved detection accuracy (selectivity), sensitivity, and stability
and even an improved discernibility of the presence of ozone by the naked
eye. In addition, by varying the kinds and formulating amounts of said
anthraquinone dye, extender, and other components, the detection
sensitivity and the speed of color change can be freely controlled, thus
enabling a still more positive detection of ozone concentration.
The ozone sensor ink of the invention undergoes fading or discoloration
upon contact with ozone even when it is a substantially dry condition, to
the extent permitting a visual detection of the presence of ozone, and is
very satisfactory in the accuracy (selectivity), sensitivity, and
stability of detection. Particularly when a cationic surfactant of the
quaternary ammonium salt type is included in the formulation, a still more
satisfactory color-change response can be obtained to permit a positive
detection of still lower concentrations of ozone. Depending on conditions,
even ozone in a low concentration of 0.03 ppm can be successfully
detected.
Furthermore, by varying the kinds and formulating amounts of the
anthraquinone dye and other components, the detection sensitivity and
color change speed of the ink of the invention can be freely controlled.
In addition, by formulating a resinous binder, the ink of the invention can
be used as a printing ink, writing ink, or a stamp ink. Moreover, the ink
can be used in the form of a paper, film or other matrix coated or
saturated with it. Thus, by forming several ink layers on a substrate
using several kinds of inks of the invention which fade or discolor at
discrete ozone levels, a convenient ozone indicator can be provided.
EXAMPLES
Example 1
Using a mixer, 0.20 part by weight of anthraquinone disperse dye [Miketon
Fast Red Violet R, Mitsui-BASF Co.], 7.35 parts by weight of
ethylcellulose resin (Ethocel 10, Dow Chemical Co.) as resinous binder,
9.80 parts by weight of silica gel [Aerosil R-972, Japan Aerosil Co.],
1.96 parts by weight of coco-alkyltrimethylammonium chloride [CA-2150,
Nikkol Co.] as cationic surfactant, and 80.69 parts by weight of
ethylcellosolve [Seahosol MG, Nippon Shokubai Co.] as solvent were mixed
uniformly to provide an ozone sensor ink.
Example 2
Except that 1.96 parts by weight of lauryltrimethylammonium chloride
[Coatamine 24P, Kao Co.] was used as cationic surfactant, the procedure of
Example 1 was otherwise repeated to provide an ozone sensor ink.
Example 3
Using a mixer, 0.24 part by weight of anthraquinone disperse dye [Miketon
Fast Turquoise Blue G, Mitsui-BASF Co.], 9.15 parts by weight of
ethylcellulose resin [Ethocel 10, Dow Chemical Co.] as resinous binder,
12.20 parts by weight of silica gel [Aerosil R-972, Japan Aerosil Co.),
2.44 parts by weight of hexadecyltrimethylammonium chloride [Cation PB-40,
Nippon Oil and Fat Co.] as cationic surfactant, and 75.97 parts by weight
of ethylcellulose [Seahosol MG, Nippon Shokubai Co.] as solvent were mixed
uniformly to provide an ozone sensor ink.
Test Example 1
The color change performance was evaluated using the inks prepared in
Examples 1-3 and Comparative Examples 1-2. Using each ink, Kent paper was
printed by silk screen (150 mesh) printing. When the print was exposed to
an atmosphere containing 0.3 ppm of ozone for about 15 minutes, the time
course of fading or discoloration of the printed color was apparent to the
unaided eye. The color difference (.DELTA.E) between the color after
exposure to ozone and the initial color before exposure (before color
change) was determined. The results are presented in Table 1.
TABLE 1
______________________________________
Color difference (.DELTA.E)
______________________________________
Example 1 43.2
Example 2 48.8
Example 3 45.6
______________________________________
It is clear from Table 1 that the color difference is large and the color
residue is small in Examples 1-3, indicating that the ozone sensor ink of
the invention is sensitive enough to detect ozone even when the
atmospheric concentration of ozone is as low as 0.3
Example 4
Using the ozone sensor ink prepared in Example 1, an ozone indicator was
fabricated. On the other hand, a regular color ink for the
non-color-change layer was prepared. Thus, 60.6 parts by weight of white
ink [Conc 061-a], 6.1 parts by weight of purple ink [082-A], and 33.3
parts by weight of medium ink [Medium] [all in the Serikol JM Series
(Matte Type), Teikoku Ink Co.] were mixed to prepare the regular color ink
(light purple color).
Using the ozone sensor ink, the character design (dropout characters)
illustrated in FIG. 3 was printed on Kent paper by silk screen (150 mesh)
printing to provide a color-change layer. Then, avoiding overlap with the
color-change layer, the character design illustrated in FIG. 4 was printed
using the regular color ink by silk screen (300 mesh) printing to provide
a non-color-change layer. In this manner, an indicator which was light
purple all over was obtained. In the practice of the invention, whichever
of the ozone sensor ink and the regular color ink can be used for the
design illustrated in FIG. 3 or the design illustrated in FIG. 4.
Moreover, it does not matter which of the designs is printed first.
The indicator obtained in the above manner was allowed to stand in an
ozone-containing atmosphere (ozone concentration about 0.3 ppm) for 15
minutes. As a result, the color-change layer consisting in said dropout
characters was s electively discolored so that the characters of the
non-color-change layer became discernible as light purple characters.
Example 5
An ozone sensor ink was first prepared. Thus, 0.24 part by weight of
anthraquinone disperse dye [Miketon Fast Red Violet R, Mitsui-BASF Co.],
9.15 parts by weight of ethylcellulose resin [Ethocel 10, Dow Chemical
Co.] as resinous binder, 12.20 parts by weight of silica gel as extender
pigment, and 78.41 parts by weight of ethylcellosolve [Seahosol MG, Nippon
Shokubai Co.] were mixed uniformly to provide an ozone sensor ink (light
purple color).
On the other hand, a regular color ink for the non-color-change layer was
prepared. Thus, 60.6 parts by weight of white ink [Conc 061-a], 6.1 parts
by weight of purple ink [082-A], and 33.3 parts by weight of medium ink
[Medium] [all in the Serikol JM Series (Matte Type), Teikoku Ink Co.] were
mixed to prepare the regular color ink (light purple color).
Using the ozone sensor ink, the character design (dropout characters)
illustrated in FIG. 3 was printed on Kent paper by silk screen (150 mesh)
printing to provide a color-change layer. Then, avoiding overlap with the
color-change layer, the character design illustrated in FIG. 4 was printed
using the regular color ink by silk screen (300 mesh) printing to provide
a non-color-change layer. In this manner, an indicator which was light
purple all over was obtained. In the practice of the invention, whichever
of the ozone sensor ink and the regular color ink can be used for the
design illustrated in FIG. 3 or the design illustrated in FIG. 4.
Moreover, it does not matter which of the designs is printed first.
The indicator obtained in the above manner was allowed to stand in an
ozone-containing atmosphere (ozone concentration: about 0.3 ppm) for 15
minutes. As a result, the color-change layer consisting in said dropout
characters was selectively discolored so that the characters of the
non-color-change layer became discernible as light purple characters.
Example 6
An ozone indicator was fabricated using the same ozone sensor ink and
regular color ink as used in Example 5.
First, the character design illustrated in FIG. 5 was printed on Kent paper
using the ozone sensor ink by silk screen (150 mesh) printing to provide a
color-change layer. Then, avoiding overlap with the color-change layer,
the character design (dropout characters) illustrated in FIG. 6 was
printed using the regular color ink by silk screen (300 mesh) printing to
provide a non-color-change layer. Thereafter, over the surface of the
non-color-change layer, the character design (fine English language text)
illustrated in FIG. 7 was printed using the ozone sensor ink by silk
screen (300 mesh) printing to provide a color-change layer. After
formation of this color-change layer, the borderline which was initially
slightly conspicuous became substantially undiscernible.
When the indicator thus obtained was left standing in an ozone-containing
atmosphere (ozone concentration: about 0.3 ppm) for 15 minutes, the
color-change layer corresponding to the English language text discolored
first, then the color-change layer corresponding to the dropout characters
(the exposed zone of the color-change layer) faded away, and finally the
white letters appeared due to contrast with the non-color-change layer.
Example 7
As the regular color ink for the non-color-change layer, 38.8 parts by
weight of white ink [Conc 061-a], 2.6 parts by weight of purple ink
[082-A], 0.9 part by weight of ultramarine blue ink [037-b], and 57.7
parts by weight of medium ink [Medium] [all in the Serikol JM Series
(Matte Type), Teikoku Ink Co.] were blended for color mixing. On the other
hand, as the ozone sensor ink, the same ink as used in Example 5 was used.
First, the ozone sensor ink was printed solid on Kent paper by silk screen
(300 mesh) printing to provide a color-change layer. Then, over the entire
surface of the color-change layer, the character design (dropout
characters) illustrated in FIG. 8 was printed using the regular color ink
by silk screen (300 mesh) printing to provide a non-color-change layer.
The resulting indicator was allowed to stand in an ozone-containing
atmosphere (ozone concentration: about 0.3 ppm) for 15 minutes. As a
result, the color-change layer corresponding to the dropout characters
(the exposed zone of the color-change layer) faded away and finally white
characters appeared due to contrast with the non-color-change layer.
Example 8
0.25 Part by weight of anthraquinone disperse dye [Miketon Fast Red Violet
R, Mitsui-BASF Co.], 6.25 parts by weight of ethylcellulose resin [Ethocel
10, Dow Chemical Co.] as resinous binder, 3.13 weight of maleic acid resin
[Malkyd 33, Arakawa Chemical Co.], 6.25 parts by weight of silica gel as
extender, and 84.12 parts by weight of ethylcellosolve as solvent were
mixed uniformly to provide an ozone sensor ink.
Example 9
0.25 Part by weight of anthraquinone disperse dye [Miketon Fast Turquoise
Blue G, Mitsui-BASF Co.], 9.38 parts by weight of ethylcellulose resin
[Ethocel 10, Dow Chemical Co.] as resinous binder, 12.50 parts by weight
of silica gel as extender, and 77.87 parts by weight of ethylcellosolve as
solvent were mixed uniformly to provide an ozone sensor ink.
Example 10
0.30 Part by weight of anthraquinone disperse dye [Miketon Fast Blue Extra,
Mitsui-BASF Co.], 6.25 parts by weight of ethylcellulose resin [Ethocel
10, Dow Chemical Co.] as resinous binder, 10.00 parts by weight of silica
gel as extender, and 83.45 parts by weight of ethylcellosolve as solvent
were mixed uniformly to provide an ozone sensor ink.
Test Example 2
The performance of the ozone sensor ink containing the anthraquinone dye in
accordance with the invention was evaluated.
Using the ozone sensor inks prepared in Examples 8-10, respectively, and
the silk screen printing technique, Kent paper was coated to prepare
samples. Those samples were exposed to ozone under the conditions shown in
Table 1 and the color change performance of each sample was grossly
evaluated. The evaluation criteria were "o" for the case in which a color
change was easily recognized and "x" for the case in which the color
change could not be easily recognized. As a color retentivity parameter,
the difference between the color immediately after color change and the
color after 3 days of subsequent standing at 50.degree. C. was determined.
The results are also shown in Table 2. For comparison's sake, the
conventional indicator (potassium iodide-starch paper) was also tested in
the same manner. The results are shown in the column of Comparative
Example 1.
TABLE 2
______________________________________
Comparative
Example Example Example Example
8 9 10 1
______________________________________
Color change per-
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
formance, 5 ppm .times.
15 min.
Color change per- .smallcircle. .smallcircle. .smallcircle. x
formance, 1 ppm .times.
15 min.
Color change per- .smallcircle. .smallcircle. .smallcircle. x
formance, 0.3 ppm .times.
15 min.
Color retention .smallcircle. .smallcircle. .smallcircle. x
after color change
______________________________________
It is clear from table 2 that the conventional indicator detects ozone
under the conditions of 5 ppm.times.15 min. but fails to detect lower
concentrations of ozone and that, in contract, the ozone sensor ink of the
invention responds sensitively to ozone even when the concentration of
ozone is as low as 1 ppm or 0.3 ppm.
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